Protobuf

C++
* Make proto2::Message::DiscardUnknownFields() non-virtual
* Separate RepeatedPtrField into its own header file
* For default floating point values of 0, consider all bits significant
* cmake: support `MSVC_RUNTIME_LIBRARY` property (8851)
* Fix shadowing warnings (8926)
* Fix for issue 8484, constant initialization doesn't compile in msvc clang-cl environment (8993)
* Fix build on AIX and SunOS (8373) (9065)
* Add Android stlport and default toolchains to BUILD. (8290)

Java
* This release drops support for Java 7. Use 3.18.x if you still need Java 7 support.
* For default floating point values of 0, consider all bits significant
* Annotate `//java/com/google/protobuf/util/...` with nullness annotations
* Use ArrayList copy constructor (7853)

Kotlin
* Switch Kotlin proto DSLs to be implemented with inline value classes

Python
* Proto2 DecodeError now includes message name in error message
* Make MessageToDict convert map keys to strings (8122)
* Add python-requires in setup.py (8989)
* Add python 3.10 (9034)

JavaScript
* Skip exports if not available by CommonJS (8856)
* JS: Comply with CSP no-unsafe-eval. (8864)

PHP
* Added "object" as a reserved name for PHP (8962)

Ruby
* Override Map.clone to use Map's dup method (7938)
* Ruby: build extensions for arm64-darwin (8232)
* Add class method Timestamp.from_time to ruby well known types (8562)
* Adopt pure ruby DSL implementation for JRuby (9047)
* Add size to Map class (8068)

C
* Correctly set ExtensionRegistry when parsing with MessageParser, but using an already existing CodedInputStream (7246)
* [C] Make FieldDescriptor propertyName public (7642)

C++
* Reduce memory consumption of MessageSet parsing
* This release addresses a [Security Advisory for C++ and Python users](https://github.com/protocolbuffers/protobuf/security/advisories/GHSA-8gq9-2x98-w8hf)

Java
* Improve performance characteristics of UnknownFieldSet parsing (9371)

Python
* Update setup.py to reflect that we now require at least Python 3.5 (8989)
* Performance fix for DynamicMessage: force GetRaw() to be inlined (9023)

Ruby
* Update ruby_generator.cc to allow proto2 imports in proto3 (9003)

C++
* Fix warnings raised by clang 11 (8664)
* Make StringPiece constructible from std::string_view (8707)
* Add missing capability attributes for LLVM 12 (8714)
* Stop using std::iterator (deprecated in C++17). (8741)
* Move field_access_listener from libprotobuf-lite to libprotobuf (8775)
* Fix 7047 Safely handle setlocale (8735)
* Remove deprecated version of SetTotalBytesLimit() (8794)
* Support arena allocation of google::protobuf::AnyMetadata (8758)
* Fix undefined symbol error around SharedCtor() (8827)
* Fix default value of enum(int) in json_util with proto2 (8835)
* Better Smaller ByteSizeLong
* Introduce event filters for inject_field_listener_events
* Reduce memory usage of DescriptorPool
* For lazy fields copy serialized form when allowed.
* Re-introduce the InlinedStringField class
* v2 access listener
* Reduce padding in the proto's ExtensionRegistry map.
* GetExtension performance optimizations
* Make tracker a static variable rather than call static functions
* Support extensions in field access listener
* Annotate MergeFrom for field access listener
* Fix incomplete types for field access listener
* Add map_entry/new_map_entry to SpecificField in MessageDifferencer. They
record the map items which are different in MessageDifferencer's reporter.
* Reduce binary size due to fieldless proto messages
* TextFormat: ParseInfoTree supports getting field end location in addition to
start.
* Fix repeated enum extension size in field listener
* Enable Any Text Expansion for Descriptors::DebugString()
* Switch from int{8,16,32,64} to int{8,16,32,64}_t

Java
* Fix errorprone conflict (8723)
* Removing deprecated TimeUtil class. (8749)
* Optimized FieldDescriptor.valueOf() to avoid array copying.
* Removing deprecated TimeUtil class.
* Add Durations.parseUnchecked(String) and Timestamps.parseUnchecked(String)
* FieldMaskUtil: Add convenience method to mask the fields out of a given proto.

JavaScript
* Optimize binary parsing of repeated float64
* Fix for optimization when reading doubles from binary wire format
* Replace toArray implementation with toJSON.

PHP
* Migrate PHP & Ruby to ABSL wyhash (8854)
* Added support for PHP 8.1 (currently in RC1) to the C extension (8964)
* Fixed PHP SEGV when constructing messages from a destructor. (8969)

Ruby
* Move DSL implementation from C to pure Ruby (8850)
* Fixed a memory bug with RepeatedField+. (8970)

Python
* Drops support for 2.7 and 3.5.

Other
* [csharp] ByteString.CreateCodedInput should use ArraySegment offset and count (8740)
* [ObjC] Add support for using the proto package to prefix symbols. (8760)
* field_presence.md: fix Go example (8788)

C++
* Fix warnings raised by clang 11 (8664)
* Make StringPiece constructible from std::string_view (8707)
* Add missing capability attributes for LLVM 12 (8714)
* Stop using std::iterator (deprecated in C++17). (8741)
* Move field_access_listener from libprotobuf-lite to libprotobuf (8775)
* Fix 7047 Safely handle setlocale (8735)
* Remove deprecated version of SetTotalBytesLimit() (8794)
* Support arena allocation of google::protobuf::AnyMetadata (8758)
* Fix undefined symbol error around SharedCtor() (8827)
* Fix default value of enum(int) in json_util with proto2 (8835)
* Better Smaller ByteSizeLong
* Introduce event filters for inject_field_listener_events
* Reduce memory usage of DescriptorPool
* For lazy fields copy serialized form when allowed.
* Re-introduce the InlinedStringField class
* v2 access listener
* Reduce padding in the proto's ExtensionRegistry map.
* GetExtension performance optimizations
* Make tracker a static variable rather than call static functions
* Support extensions in field access listener
* Annotate MergeFrom for field access listener
* Fix incomplete types for field access listener
* Add map_entry/new_map_entry to SpecificField in MessageDifferencer. They
record the map items which are different in MessageDifferencer's reporter.
* Reduce binary size due to fieldless proto messages
* TextFormat: ParseInfoTree supports getting field end location in addition to
start.
* Fix repeated enum extension size in field listener
* Enable Any Text Expansion for Descriptors::DebugString()
* Switch from int{8,16,32,64} to int{8,16,32,64}_t

Java
* Fix errorprone conflict (8723)
* Removing deprecated TimeUtil class. (8749)
* Optimized FieldDescriptor.valueOf() to avoid array copying.
* Removing deprecated TimeUtil class.
* Add Durations.parseUnchecked(String) and Timestamps.parseUnchecked(String)
* FieldMaskUtil: Add convenience method to mask the fields out of a given proto.

JavaScript
* Optimize binary parsing of repeated float64
* Fix for optimization when reading doubles from binary wire format
* Replace toArray implementation with toJSON.

PHP
* Migrate PHP & Ruby to ABSL wyhash (8854)

Ruby
* Move DSL implementation from C to pure Ruby (8850)

Python
* Drops support for 2.7 and 3.5.

Other
* [csharp] ByteString.CreateCodedInput should use ArraySegment offset and count (8740)
* [ObjC] Add support for using the proto package to prefix symbols. (8760)
* field_presence.md: fix Go example (8788)